Real time scene change detection in video sequences

ABSTRACT

An apparatus configured to process a digital video signal comprising an input circuit, a processing circuit and an encoder circuit. The input circuit may be configured to present a digital video signal comprising a plurality of frames. The processing circuit may be configured to detect scene changes in the digital video signal by analyzing (i) a current one of the plurality of frames and (ii) two or more other frames. The encoder circuit may be configured to generate an encoded signal in response to the digital video signal and the scene changes. The two or more other frames may comprise (i) a first window of frames that are processed before the current frame and (ii) a second window of frames that are processed after the current frame. The processing circuit may also detect the scene changes by analyzing changes between the first window and the second window.

This is a continuation of U.S. Ser. No. 10/603,009, filed Jun. 24, 2003U.S. Pat. No. 7,313,183.

FIELD OF THE INVENTION

The present invention relates to processing digital video generally and,more particularly, to a real time scene change detection in videosequences.

BACKGROUND OF THE INVENTION

Conventional approaches for detecting scene changes analyze the recordedbitstream. Such analysis may use the results of a discrete cosinetransform (DCT) or the particular type of macroblock. Such conventionalapproaches are discussed in (i) U.S. Pat. No. 5,774,593 entitled“Automatic scene decomposition and optimization of MPEG compressedvideo”, (ii) U.S. Pat. No. 5,493,345 entitled “Method for detecting ascene change and image editing apparatus”, and (iii) U.S. Pat. No.5,642,174 entitled “Scene change detecting device”. Such conventionalapproaches do not detect scene changes before encoding the currentframe, but rather provide post-recording scene change detection.

Other conventional approaches are based on the variation of statisticsrelated to the video sequence. Different types of statistics are used,but such approaches base the detection of a scene change on thevariation of that statistic from one frame to the other, usually bycomparing the difference of statistics to a threshold.

Such approaches are discussed in U.S. Pat. No. 5,404,174, entitled“Scene change detector for detecting a scene change of a movingpicture”. This method compares the frame activity from one frame to theother. Another approach is presented in U.S. Pat. No. 5,732,146,entitled “Scene change detecting method for video and movie”. Thismethod compares the value of a histogram from one frame to the other.Another approach is discussed in U.S. Pat. No. 5,990,980, entitled“Detection of transitions in video sequences”. This method introduces adissimilarity measure based on the difference of histograms betweenconsecutive frames. Another approach is discussed in U.S. Pat. No.5,617,149, entitled “Apparatus an method for detecting scene changesusing the difference of MAD between image frames”. This method detectsscene changes when the variation of the frame based DC value is biggerthan a set threshold. Another approach is discussed in U.S. Pat. No.5,589,884, entitled “Adaptive quantization controlled by scene changedetection”. This method detects scene changes using a pixel basedvariation of DC between two consecutive frames. Another approach isdiscussed in U.S. Pat. No. 6,014,183, entitled “Method and apparatus fordetecting scene changes in a digital video stream”. This methodscompares pixel colors from one frame to the next frame to detect scenechanges. Each of these approaches is based on a first order ofderivation of the statistics used (i.e., DC, histogram, activity, etc.),and are fairly prone to invalid scene change detection.

Referring to FIG. 1, a diagram illustrating a conventional sequence ofscene changes is shown. Clear discontinuities are shown as a transition10 and a transition 12. The discontinuities between scenes (i.e., thetransition 10 between a SCENE1 and a SCENE2 and the transition 12between the SCENE2 and the SCENE3) are clear when monitoring thesequence.

Referring to FIG. 2, a diagram illustrating a conventional scene changeand a fade out is shown. The discontinuities are shown at a transition20 and a transition 22. The signal INPUT′ represents a first orderderivative of the signal INPUT. The signal INPUT″ illustrates a secondorder derivative of the signal INPUT.

Referring to FIG. 3, a diagram illustrating a conventional scene changeis shown. A first direction 30 illustrates a transition between a SCENE1and a SCENE2. A second direction 32 illustrates a transition from theSCENE2 to the SCENE1. The transition has different characteristics inthe direction 30 than in the direction 32. Conventional approaches onlyanalyze the signal INPUT(T) in either the direction 30 from onedirection than from the other direction.

Referring to FIG. 4, a diagram illustrating three conventional scenechange cases is shown. Case 1 represents a scene change from arelatively fixed input value to a relatively fixed value. Case 2illustrates a transition from a variable input value (i.e., scene 1) toa relatively fixed input value (i.e., scene 2). Case 3 illustrates arelatively fixed input value (i.e., scene 1) to a variable input value(i.e., scene 2).

It would be desirable to detect scene changes within a video sequencethat (i) distinguishes between fades and discontinuities, (ii) selects aprocessing direction to minimize processing needs and/or (iii) processeswhile recording the video sequence.

SUMMARY OF THE INVENTION

The present invention concerns an apparatus configured to process adigital video signal comprising an input circuit, a processing circuitand an encoder circuit. The input circuit may be configured to present adigital video signal comprising a plurality of frames. The processingcircuit may be configured to detect scene changes in the digital videosignal by analyzing (i) a current one of the plurality of frames and(ii) two or more other frames. The encoder circuit may be configured togenerate an encoded signal in response to the digital video signal andthe scene changes. The two or more other frames may comprise (i) a firstwindow of frames that are processed before the current frame and (ii) asecond window of frames that are processed after the current frame. Theprocessing circuit may detect the scene changes by analyzing changesbetween the first window and the second window.

The objects, features and advantages of the present invention includeproviding real time scene change detection in a video sequence that may(i) provide scene change information to a rate control circuit, (ii)adjust a bit budget for each frame, (iii) change the picture type beforerecording to achieve better general recording quality, (iv) detect scenecuts within the video sequence, but avoid detecting fades-in andfades-out that may need to be handled in a different manner and/or (v)index various existing scenes within a video sequence be used within thecontext of video editing.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will be apparent from the following detailed description andthe appended claims and drawings in which:

FIG. 1 is a diagram illustrating conventional scene changes with cleardiscontinuities;

FIG. 2 is a diagram illustrating conventional scene changes with a fadeout;

FIG. 3 is a diagram illustrating conventional scene change wheredetection has different characteristics depending on the direction;

FIG. 4 is a block diagram illustrating three conventional scene changecases;

FIG. 5 is a diagram illustrating a window of frames;

FIG. 6 is a diagram illustrating scene changes in accordance with apreferred embodiment of the present invention;

FIG. 7 is a diagram of a process illustrating a scene changes detectprocess in accordance with the present invention;

FIG. 8 is a block diagram illustrating the blending of variationsbetween frames;

FIG. 9 is a block diagram illustrating possible scene change relative tothe time between frames;

FIG. 10 is a block diagram illustrating a scene change between twoframes; and

FIG. 11 is a block diagram illustrating a scene change occurrencebetween the top and the bottom field of the same frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be used to detect scene change in a videosequence. The present invention may be used to take advantage ofhistoric statistics within a scene in a digital video signal to reducethe processing needed for encoding the video signal. Statistics withinthe video signal may be used to characterize a particular scene todistinguish one scene from another scene. The statistics may be used todistinguish a first type of transition (e.g., a real scene cut) from asecond type of transition (e.g., a fade). The applications for thepresent invention may range from navigation purposes to encoder qualityimprovement.

Referring to FIG. 5, a diagram illustrating a portion of a video signalin accordance with a preferred embodiment of the present invention isshown. A portion 100 illustrates a window of frames 102 a-102 n, where nis an integer. The frames 102 a-102 n may represent frames withindigitized video signal. The digitized video signal may be either aninterlaced signal or a progressive signal. In general, each of theframes 102 a-102 n represents 1/30 of a second. However, the particularnumber of frames per second may be adjusted to meet the design criteriaof a particular implementation. For example, a film based video signalmay have 24 frames per second.

The frame 102 f may also be referred to in a time-based sense as frame(t). The particular number of the frames 102 a-102 n used before orafter the frame 102 f may be a window. A window 110 may be defined as anumber of frames 102 a-102 n (e.g., frames 102 a-102 e). The number offrames in the window 110 may be programmable. The window 110 may also bedefined in a time-based sense as the frames (t−1 . . . t−5). A window112 may be defined as the frames 102 g-102 n. The number of frames inthe window 112 may be programmable. The window 112 may also be definedin a time-based sense as the frames t+1 . . . t+5.

A portion 120 illustrates a definition of terms within a frame. Forexample, the frame(t) is shown broken into a first field (e.g.,TOP_FIELD(t)) and a second field (e.g., BOTTOM_FIELD(t)). The fieldTOP_FIELD(t) generally comprises a parameter (e.g., DC_TOP_FIELD(t)) anda parameter (e.g., HORIZONTAL_ACTIVITY_TOP_FIELD(t). The fieldBOTTOM_FIELD(t) generally comprises a parameter (e.g.,DC_BOTTOM_FIELD(t) and a parameter (e.g.,HORIZONTAL_ACTIVITY_BOTTOM_FIELD(t). The parameters may be used toprocess the frame(t) (to be described in detail in connection with FIGS.6-11). The parameters may also be referred to as field measureparameters.

Referring to FIG. 6, a block diagram of a system 150 is shown. Thesystem 150 may be used to detect scene changes in a video signal. Thesystem 150 generally comprises an input section (or circuit) 152, aprocessing section (or circuit) 154, an encoding section (or circuit)156 and a recording section (or circuit) 158. The various components ofthe present invention are described as blocks, sections and/or circuits.However, the various components may be implemented in hardware, softwareor a combination of hardware and software. Software may be used todescribe firmware, VHDL code, etc.

The input section 152 generally comprises a stored digital video section160, a digital video capture section 162, a decoded digital videosection 164 and a multiplexer 166. The section 160 may present a signalstored on a hard-disk or other storage system. The digital video capturesection 162 may be used to digitize an analog video source. The decodeddigital video section 164 may present a signal from a video decoder. Themultiplexer 166 may present one of the video sources 160, 162 and 164 tothe processing section as a video signal (e.g., VID). The signal VID maybe either a progressive scan signal or an interlaced signal. Theprocessing section 154 may be implemented as a scene detect block (orcircuit).

The processing block 154 generally comprises a control block (orcircuit) 170, a frame buffer block (or circuit) 172, an equationcalculation block (or circuit) 174 and a configuration block (orcircuit) 176. The frame buffer 172 generally holds the necessarydigitized frames needed for equation processing. The frame buffer 172may also hold a subset of the frames 102 a-102 n if the field measureparameters are available for the specific frame. For example, if thesystem 150 needs a scene change detect as soon as available, the soonestthe scene change detect can be available is within 1/30th of the time(in a 30 frame per second implementation) after the current frame, whenmoving forward through the frames 102 a-102 n. When moving backwardsthrough the frames 102 a-102 n, information from the previous frames maybe needed. For example, if information from the previous 5 frames 102a-102 n is needed, then five 1/30th intervals may be needed. The system150 may delay the frames sent to the encoder 156 to allow the scenechange detect to arrive at or before the particular one of the frames102 a-102 n that represents the scene change. Such a latency may beintroduced by holding or buffering the frames 102 a-102 n presented tothe encoder 156. For example, if the encoder 156 benefits from the scenechange detect signal SCD arriving at the same time as the particular oneof the frames 102 a-102 n that represents the scene change detect, asingle frame would be buffered before being presented to the encoder 156through the path 180. The path 180 may be an optional path from theframe buffer 172 to the encoder 156.

The equation calculation block 174 generally calculates the fieldmeasure parameters from each of the frames 102 a-102 n and executes eachof the equations needed to assess scene change. The configuration block176 may be used to configure the scene change detect function with oneor more parameters. Such parameters may include window size (e.g., thenumber of frames prior to and after the current frame), a detectthreshold (e.g., the level of indicator values that will cause a scenechange detect) or other parameters. The encoder 156 may receive an inputfrom either the multiplexer 166 or the processing circuit 154. Theencoder 156 may benefit from the scene change detect in terms ofoptimizing rate control by adjusting the bit budget per frame and/orchanging the picture type. The encoder 156 may also benefit from theprocessing circuit in terms of enabling and indexing existing scenes forediting, navigation and/or other applications.

The recording section 158 is generally an optional section configured tostore the encoded video (e.g., ENC) presented by the encoder circuit156. Additional features, such as transporting the encoded signal ENC,may also be implemented. Additionally, the encoder 156 may be bypassedif needed. In particular, the signal VID may be directly recorded by therecording section 158. In such a configuration, the signal VID may beedited or navigated with detect scene change information represented assideband information.

Referring to FIG. 7, a diagram of a method (or process) 200 illustratingscene change detection in accordance with a preferred embodiment of thepresent invention is shown. The method 200 generally comprises a step202, a step 204, a step 206, a step 208, a step 210, a step 212, a step214, and a step 216. The step 204 generally calculates the fieldmeasures. The step 206 generally calculates the second orderderivatives. The step 208 generally calculates the averages of thesecond order derivatives. The step 210 calculates statistical variationscompared to the calculated averages from step 208. The step 212generally calculates scene change indicators. The step 214 generallychecks if a scene change has occurred between two distinct frames 102a-102 n or in the middle of one of the frames 102 a-102 n.

The frame buffer 172 may be implemented as a memory configured to storethe frames 102 a-102 n. The frame buffer 172 may also store relevantframe information that may be used by the equations section 174. In thestep 204, the field measure parameters may be calculated on each of theframes 102 a-102 n. The field measure parameters may be used by theequation calculation block 174. A configuration parameter (e.g.,RESOLUTION) may be used by the step 210. A configuration parameter(e.g., THRESHOLD) may be used by the step 214. In the step 216, if aparticular one of the frames 102 a-102 n is no longer needed, theparticular frame is generally shifted out and another one of the frames102 a-102 n is generally shifted in.

The present invention generally uses two field measure parameters. TheDC parameters generally represent a sum of the color corrected luma pel.The horizontal activity generally represents a sum of the absolutedifferences between horizontally adjacent color corrected luma pels. Ifa scene change occurred on the frame(t), the system 150 has access tothe frames t-window-size to t+widow-size measure parameters. In oneexample, a window-size of five may be assigned. To simplify thefollowing equations, the following definitions may be used:input[0](t)=DC_Top_Field(t)input[1](t)=DC_Bottom_Field(t)input[2](t)=Horizontal_Activity_Top_Field(t)input[3](t)=Horizontal_Activity_Bottom-Field(t)

Some continuous measures during a sequence are generally expected.Discontinuities that may occur on a scene change boundary are generallysearched. In general, the present invention is based on a second orderderivative of the frames 102 a-102 n.

A scene change may be seen in two ways (e.g., a scene change from SCENE1to SCENE2 or from SCENE2 to SCENE1). In some cases, a scene change ismore obvious from one point of view. To perform the scene changedetection, a second order derivative of the input[ ](t) may beimplemented. A scene change may be checked from SCENE1 to SCENE2, usinga left second order derivative and vice versa. Such derivatives may beimplemented in the equation block 174. The following equationsillustrate such derivatives:

left first order derivativeinput′_(l) [i](t)=input[i](t)−input[i](t−1)  EQ1right first order derivativeinput′_(r) [i](t)=input[i](t+1)−input[i](t)  EQ2left second order derivativeinput″_(r) [i](t)=input′_(r) [i](t)−input′_(r) [i](t−1)  EQ3right second order derivativeinput″_(r) [i](t)=input′_(r) [i](t+1)−input′_(r) [i](t)  EQ4iε{0, 1, 2, 3}

Three major scene change may be present (as shown in FIG. 4). In typicalcase 1, both approaches generally have a large increase of the secondorder derivative. In the typical case 2, a large increase of input″_(r)[] (t) from SCENE2 to SCENE1 may be present, but no increase ofinput″_(l)[ ] (t) from SCENE1 to SCENE2. In the typical case 3, a largeincrease of input″_(l)[ ] (t) from SCENE1 to SCENE2 may be present, butno increase of input″_(r)[ ] (t) from SCENE2 to SCENE1.

The present invention generally isolates the increases/variations of thesecond order variations. The following equations quantify suchvariations:

$\begin{matrix}{{{{average}_{r}\lbrack i\rbrack}(t)} = {\frac{\sum\limits_{j = 0}^{2}{{{{input}_{r}^{\prime\prime}\lbrack i\rbrack}\left( {t + j} \right)}}}{3}r}} & {{EQ}\mspace{14mu} 5} \\{{{{average}_{l}\lbrack i\rbrack}(t)} = \frac{\sum\limits_{j = 1}^{3}{{{{input}_{l}^{\prime\prime}\lbrack i\rbrack}\left( {t - j} \right)}}}{3}} & {{EQ}\mspace{14mu} 6} \\{{{{variation}\lbrack i\rbrack}(t)} = {\frac{{{{input}_{r}^{\prime\prime}\lbrack i\rbrack}\left( {t - 1} \right)}}{{{cst}\lbrack i\rbrack} + {{{average}_{r}\lbrack i\rbrack}(t)}} + \mspace{40mu}{\frac{{{{input}_{l}^{\prime\prime}\lbrack i\rbrack}(t)}}{{{cst}\lbrack i\rbrack} + {{{average}_{l}\lbrack i\rbrack}(t)}}\mspace{11mu} i\; ɛ\left\{ {0,1,2,3} \right\}}}} & {{EQ}\mspace{14mu} 7}\end{matrix}$In general, cst[i] is a constant defined as a function of the resolutionand the input type (e.g., DC or Activity). The constant cst[i] shouldroughly give an estimation of what background variation level isexpected. The higher the constant cst[i], the less the present inventionwill be sensitive to incorrect detection in case of a very static videosequence. However, the present invention may be less sensitive to somesubtile scene changes.

Instead of checking each result independently, the system 150 combinesall of the results and normalizes the result. If all the differentvariations cannot pinpoint a scene change when they are analyzedindependently, an analysis of the aggregate may indicate that a scenechange occurred. Such aggregate analysis may allow detection of lessobvious scene change. An aggregate analysis may also allow analysiswithout being overly sensitive to each individual variation.

Combining data contemplates different possible scene changeconfigurations. A scene change can occur between 2 frames, but may alsooccur between the top and the bottom field of a particular frame 102a-102 n (e.g., in a top field first configuration, and vice versa for abottom field first configuration).

Scene change detection from the top and bottom field point of view doesnot generally occur at the same time. If the scene change occurs betweentwo of the frames 102 a-102 n, the variation appears at the same timefrom the top and bottom field point of view. If the scene change occursin the middle of a frame, then the variation appears one frame earlierfor the bottom field inputs in a Top Field First configuration (and viceversa in a bottom field first configuration).

Scene change indicators between the frames 102 a-102 n may be defined bythe following equations:

$\begin{matrix}{{{Frame}\; 1\;{Indicator}} = \frac{{{{variation}\lbrack 0\rbrack}(t)} + {{{variation}\lbrack 2\rbrack}(t)}}{4}} & {{EQ}\mspace{14mu} 8} \\{{{Frame}\; 2\;{Indicator}} = \frac{{{{variation}\lbrack 1\rbrack}(t)} + {{{variation}\lbrack 3\rbrack}(t)}}{4}} & {{EQ}\mspace{14mu} 9}\end{matrix}$

Scene change indicators in a particular one of the frames 102 a-102 nmay be defined by the following equations:

$\begin{matrix}{{{Field}\; 1{Indicator}} = \frac{{{{variation}\lbrack 0\rbrack}\left( {t + 1} \right)} + {{{variation}\lbrack 2\rbrack}\left( {t + 1} \right)}}{4}} & {{EQ}\mspace{14mu} 10} \\{{{Field}\; 2\;{Indicator}} = \frac{{{{variation}\lbrack 1\rbrack}(t)} + {{{variation}\lbrack 3\rbrack}(t)}}{4}} & {{EQ}\mspace{14mu} 11}\end{matrix}$

The following equations represent a final output:((FramelIndicator+Frame2Indicator)>=Threshold&&(2*min(FramelIndicator,Frame2Indicator)>=max(FramelIndicator,Frame2Indicator))  EQ12((FieldlIndicator+Field2Indicator)>=Threshold&&(2*min(FieldlIndicator,Field2Indicator>=max(FieldlIndicator,Field2Indicator))  EQ13The equations EQ12 and EQ13 return a boolean output. If the equationEQ12 is true, then a scene change has been detected between frame (t)and the frame (t−1). If the equation EQ13 is true, then a scene changehas been detected between the two fields of the frame (t). The equationsEQ12 and EQ13 also check that a scene change is noticeable on the twodistinct fields.

A value for the threshold in step 214 defines the sensitivity of themethod 200. The larger the value of the threshold, the more scene changewill be missed. The smaller the value of the threshold, the moreincorrect scene change will be detected.

Referring to FIG. 8, a diagram illustrating the blending of variationsbetween the frames 102 a-102 n is shown. The variations between windowframes before and after the frame(t) may be blended and normalized basedon a second order derivative equation. For example, the second orderderivative equation may allow the detection of less obvious scenechanges. The equation EQ7 may be used to calculate the variation, whichmay process absolute input values relative to an average. The results ofthe variation equations are shown in the graphs 220 and 222. A globalanalysis is shown in the graphs 230 and 232. The results may bepresented to the indicator equations EQ8, EQ9, EQ10 and EQ11. The resultof the aggregate variation (e.g., the sum of processed deltas) may becompared to a threshold as in equations EQ12 and EQ13.

Referring to FIGS. 9, 10, and 11, a diagram illustrating the frames 102e, 102 f and 102 g is shown. Each of the frames 102 e, 102 f and 102 gcomprises a top field and a bottom field. A top field firstconfiguration may be shown. The top field may be available in timebefore the bottom field on all frames. The frame 102 f may represent aframe occurring at a time t. The frame 102 e may represent a frameoccurring at a time t−1 (e.g., one time slot before the time t). Theframe 102 g may represent a frame occurring at a time t+1 (e.g., onetime slot after the time t).

In FIG. 9, a diagram illustrating possible scene change SC1 and SC2 isshown. The scene changes SC1 occur at the time between frames. Forexample, the scene changes SC1 may occur between the frames 102 e, 102 for 102 g. The scene changes SC2 may occur between the top and bottomfield of a particular one of the frames 102 e, 102 f or 102 g.

In FIG. 10, a scene change occurrence 240 between the frame 102 e andthe frame 102 f is shown. The scene change 240 may first be representedin the top field of the frame 102 f. The indicator equations EQ8 and EQ9may be used to process such a scene change.

In FIG. 11, a scene change 242 is shown occurring at a time between thetop and bottom field of the frame 102 f. The scene change 242 may firstbe represented in the digital video bottom field of the frame 102 f. Thescene change 242 may then be represented in the digital video top fieldof the frame 102 g. In this case, the indicator equations EQ10 and EQ11may be used to blend the variations in a way that provides appropriatesensitivity to the scene change detect mechanism.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention.

1. An apparatus configured to process a digital video signal comprising:an input circuit configured to present a digital video signal comprisinga plurality of frames; a processing circuit configured to detect scenechanges in said digital video signal by analyzing (i) a current one ofsaid plurality of frames and (ii) two or more other frames; and anencoder circuit configured to generate an encoded signal in response tosaid digital video signal and said scene changes, wherein (a) said twoor more other frames comprise (i) a first window of frames that areprocessed before said current frame and (ii) a second window of framesthat are processed after said current frame and (b) said processingcircuit detects said scene changes by analyzing changes between saidfirst window and said second window.
 2. The apparatus according to claim1, further comprising: a storage circuit configured to record saidencoded signal.
 3. The apparatus according to claim 1, wherein saidinput circuit is configured to generate said digital video signal inresponse to either (i) a stored signal, (ii) a captured signal, or (iii)a decoded signal.
 4. The apparatus according to claim 1, wherein eachframe comprises 1/30 of a second.
 5. The apparatus according to claim 1,wherein a transition signal comprises information used by said encoderto simplify generating said encoded signal.
 6. A method for processingvideo, comprising the steps of: (A) receiving a video signal comprisinga plurality of frames; (B) generating one or more transition signals inresponse to (i) a current one of said frames, (ii) one or more framesthat are processed before said current frame and (iii) one or moreframes that are processed after said current frame; (C) calculating asecond order derivative of a first transition from a first scene to asecond scene; and (D) generating an encoded signal in response to (i)said video signal and (ii) said transition signals.
 7. The methodaccording to claim 6, wherein step (B) further comprises: calculating asecond order derivative of a second transition from a second scene to afirst scene.
 8. The method according to claim 7, wherein step (B)further comprises: calculating a first average of said one or moreframes that are processed before said current frame.
 9. The methodaccording to claim 8, wherein step (B) further comprises: calculating asecond average of said one or more frames that are processed before saidcurrent frame.
 10. The method according to claim 9, wherein step (B)further comprises: calculating a statistical variation compared to saidfirst and second averages.
 11. The method according to claim 10, whereinstep (B) further comprises: generating a scene change indicator inresponse to said variation.
 12. The method according to claim 6, whereinsaid transition signals comprise information used by an encoder tosimplify generating said encoded signal.
 13. The method according toclaim 6, further comprising the step of: recording said encoded signal.14. The method according to claim 6, wherein step (A) generates saidvideo signal in response to (i) a stored signal, (ii) a captured signal,or (iii) a decoded signal.
 15. The method according to claim 6, whereinstep (B) comprises: generating field measures in response to saidplurality of frames.